Beyond the mountain bike trails of Derby are remnants of the town’s beginnings as a tin mine.

Its glory years were the 1880-90s, when it was the richest tin mine in this corner of the state, cranking out 120 tonnes of tin a month.

Mining continued (through the Briseis mine) until 1948, but after the floods of 1929 that essentially wiped out the town, tin mining was dwindling.

Like many parts of Tasmania, on the surface, there is not a lot of physical evidence that belies the past productivity of the town.

There’s the Cascade Dam and the Mount Paris Dam. But barely signposted yet still easily accessible is the Derby Tunnel.

The Sunday Examiner team visited the site to find out more about Derby’s lesser-known attractions.

At one stage, tunnels were common in Derby, as part of the tin mining industry. All of them, except this one, have been filled in or destroyed.

It was built in the late 1800s to wash away tailings from the mine site. It was the means to an end of a feud between three companies couldn’t decide how to dispose of the byproduct.

So one mine’s management took it upon themselves to drill on through the granite to make a tunnel, and that was that.

It took four years to create, and stretches 2000 feet in length (about 600 metres).

The tunnel is accessed by car off the main road – past the entrance to the Blue Derby Trails, and on the same side of the road, just over the bridge.

It’s a short, easy walk from the small carpark down to the tunnel entrance.

The path meanders above the Cascade River, and intersects at some points with parts of the new bike trails.

You’ll know you’ve reached the tunnel because it’s signposted by a rusted mine cart that’s slowly been overtaken by lichen and moss.

There are also piles and piles of old tailings (rocks) as you get closer to the tunnel. These too have been transformed by creeping greenery.

The tunnel entrance itself is shrouded by ferns, and on this particular day, it’s holding a cloud of mist.

Cavernous to begin with, the tunnel narrows and eventually becomes pitch black as one ventures a few hundred metres in.

By torchlight, old sleepers are still visible underfoot.

Those who are brave enough to turn their torchlights off will also find a strong population of glow worms.

It’s also said to be home to Tasmanian cave spiders, but thankfully none make an appearance to the Sunday Examiner team.

It is, by all reports, possible to make it to the end of the tunnel but it’s advised to wear gumboots. The lower half of the tunnel can gather reasonably deep pools of water – as photographer Phillip Biggs discovered first hand.

The tunnel walk, while unchallenging, is riddled with tripping hazards, and the aforementioned puddles.

Recommended equipment: a torch, gum boots, and for photographers, tripods and flashes.